using System;
using System.Diagnostics;
using System.IO;

namespace Org.BouncyCastle.Utilities.IO
{
	public abstract class BaseInputStream : Stream
	{
		private bool closed;

		public sealed override bool CanRead { get { return !closed; } }
		public sealed override bool CanSeek { get { return false; } }
		public sealed override bool CanWrite { get { return false; } }
		public override void Close() { closed = true; }
		public sealed override void Flush() {}
		public sealed override long Length { get { throw new NotSupportedException(); } }
		public sealed override long Position
		{
			get { throw new NotSupportedException(); }
			set { throw new NotSupportedException(); }
		}

		public override int Read(byte[] buffer, int offset, int count)
		{
			int pos = offset;
			try
			{
				int end = offset + count;
				while (pos < end)
				{
					int b = ReadByte();
					if (b == -1) break;
					buffer[pos++] = (byte) b;
				}
			}
			catch (IOException)
			{
				if (pos == offset) throw;
			}
			return pos - offset;
		}

		public sealed override long Seek(long offset, SeekOrigin origin) { throw new NotSupportedException(); }
		public sealed override void SetLength(long value) { throw new NotSupportedException(); }
		public sealed override void Write(byte[] buffer, int offset, int count) { throw new NotSupportedException(); }
	}
}
